ADS1291_14 Datasheet, PDF (7/75 Pages) Texas Instruments – Power, 2-Channel, 24-Bit Analog Front-End for Biopotential Measurements

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ADS1291
ADS1292
ADS1292R
SBAS502B – DECEMBER 2011 – REVISED SEPTEMBER 2012
PARAMETER MEASUREMENT INFORMATION
NOISE MEASUREMENTS
The ADS1291, ADS1292, and ADS1292R noise performance can be optimized by adjusting the data rate and
PGA setting. As the averaging is increased by reducing the data rate, the noise drops correspondingly.
Increasing the programmable gain amplifier (PGA) value reduces the input-referred noise, which is particularly
useful when measuring low-level biopotential signals. Table 1 through Table 8 summarize the ADS1291,
ADS1292, and ADS1292R noise performance. The data are representative of typical noise performance at T_A =
+25°C. The data shown are the result of averaging the readings from multiple devices and are measured with the
inputs shorted together. For the shown data rates, the ratio is approximately 6.6.
Table 1 through Table 8 show measurements taken with an internal reference. The data are also representative
of the ADS1291, ADS1292, and ADS1292R noise performance when using a low-noise external reference such
as the REF5025.
In Table 1 through Table 8, µV_RMS and µV_PP are measured values. SNR, noise-free bits, ENOB, and dynamic
range are calculated with Equation 1, Equation 2, and Equation 3.
SNR = ENOB ´ 6.02
(1)
Noise-Free Bits = 2 log
2 V_REF
Gain ´ Peak-to-Peak Noise
(2)
ENOB = 2 log
V_REF
2 ´ Gain ´ RMS Noise
(3)
Table 1. Input-Referred Noise (μV_RMS / μV_PP) 3-V Analog Supply and 2.42-V Reference⁽¹⁾
DR BITS
OF
CONFIG1
REGISTER
000
001
010
011
100
101
110
111
OUTPUT
DATA
RATE
(SPS)
125
250
500
1000
2000
4000
8000
NA
–3-dB
BANDWIDTH
(Hz)
32.75
65.5
131
262
524
1048
2096
NA
μV_RMS
1.5
2.2
3.0
4.6
10.1
55.2
287.3
—
PGA GAIN = 1
μV_PP
10.3
SNR
121.0
NOISE-
FREE
BITS
18.83
14.4
117.8
18.34
18.9
115.1
17.95
30.8
111.3
17.25
99
104.5
15.57
563
89.7
13.06
2930
75.4
10.68
—
—
—
ENOB
20.10
19.58
19.11
18.49
17.36
14.91
12.53
—
μV_RMS
0.8
1.2
1.7
2.5
5.3
26.0
144.1
—
PGA GAIN = 2
μV_PP
5.6
SNR
120.0
NOISE-
FREE
BITS
18.71
7.5
117.1
18.29
10.9
113.9
17.75
15.6
110.6
17.23
48
104.0
15.60
265
90.3
13.14
1470
75.4
10.67
—
—
—
(1) At least 1000 consecutive readings were used to calculate the peak-to-peak noise values in this table.
ENOB
19.94
19.46
18.91
18.37
17.28
15.00
12.52
—
Table 2. Input-Referred Noise (μV_RMS / μV_PP) 3-V Analog Supply and 2.42-V Reference⁽¹⁾
DR BITS
OF
CONFIG1
REGISTER
000
001
010
011
100
101
110
111
OUTPUT
DATA
RATE
(SPS)
125
250
500
1000
2000
4000
8000
NA
–3-dB
BANDWIDTH
(Hz)
32.75
65.5
131
262
524
1048
2096
NA
μV_RMS
0.6
0.9
1.3
1.9
3.7
17.0
91.9
—
PGA GAIN = 3
μV_PP
4.1
SNR
119.2
NOISE-
FREE
BITS
18.58
5.5
115.9
18.15
7.7
113.0
17.67
12.0
109.5
17.02
31
103.7
15.65
173
90.5
13.18
937
75.8
10.74
—
—
—
ENOB
19.80
19.26
18.77
18.19
17.23
15.03
12.59
—
μV_RMS
0.5
0.8
1.1
1.6
2.9
12.2
66.8
—
PGA GAIN = 4
μV_PP
3.4
SNR
117.9
NOISE-
FREE
BITS
18.42
5.0
114.8
17.88
6.6
111.9
17.47
10.3
108.7
16.83
23
103.2
15.69
124
90.8
13.24
681
76.1
10.78
—
—
—
(1) At least 1000 consecutive readings were used to calculate the peak-to-peak noise values in this table.
ENOB
19.58
19.07
18.59
18.06
17.14
15.09
12.63
—
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